|Sand transport modelling in the IJzer estuary using TELEMAC-2D and SISYPHE|
Decrop, B. (2005). Sand transport modelling in the IJzer estuary using TELEMAC-2D and SISYPHE. MSc Thesis. Katholieke Universiteit Leuven (KUL)/Vrije Universiteit Brussel: Brussel. viii, 97 pp.
Modelling; Sand transport; Tidal environment; Tidal flats; ANE, Belgium, IJzer R. [Marine Regions]; Marine
A small estuary at the mouth of the IJzer river has a history of human activity and bank development. After being classified as valuable landscape and later as nature reserve, the Flemish government (AMINAL) worked on the restoration of the tidal flat and salt marshes for which concrete structures have been demolished. This study is part of the continued research into the behavior of this 'reconstructed' tidal flat of which sediment transport is an important aspect. It determines the elevation changes which will -or will not- allow the important wetting and drying event to continue.
A2DH numerical sand transport model has been set up using SISYPHE, which is a module of the TELEMAC-2D system. Since SISYPHE has never been used in the Hydraulics Laboratory of KULeuven, some test cases were required to investigate the functioning of the modeling software and to set up the correct steering file structure. Based on bathymetric and DEM measurements, GIS has been applied to merge the different data sets and to interpolate the irregularly spread data points. With this information a finite element grid has been set up stretching from an open boundary in the North Sea up to the locks and gates system hydraulically sealing the estuary from the IJzer river most of the time. Application of recorded tidal elevations during a one month simulation period produced the consequent bed elevation changes.
Thorough analysis of results produced by the test cases provided me with the insight that the modeling software is subject to numerical issues related to wetting and drying of the tidal flat, continuously changing the boundary. Overestimation of the downslope sand transport is probably the consequence. Adaptation of the software is required if future releases will not include changes to solve this issue. A one month simulation showed that sand is mainly transported from tidal flat to channel (tidal flat erosion). However, variations of tidal flat elevation need to be measured at different points in time to calibrate this complex model.